An International Mobile Subscriber Identity (IMSI) number enables international roaming of cellular phones. Each IMSI number includes a first set of digits associated with a mobile country code, a second set of digits associated with a mobile network code, and a third set of digits associated with a wireless carrier of a particular country. International roaming often involves a wireless carrier from a roaming country communicating data to a wireless carrier of a home country for authentication of mobile subscriber information. After authentication, a roaming device can receive incoming calls and make outgoing calls. However, calls to the roaming device are charged at international roaming rates, resulting in expensive calls.